The mechanism of insulin's interaction with it specific receptors in the plasma membrane of the rat adipose cell is under investigation through 1) the development of a mathematical model of the complex kinetics of insulin binding and degradation, and 2) an examination of insulin receptor internalization. A further characterization of the insulin-induced translocation of glucose transport systems from a large intracellular pool to the plasma membrane in the rat adipose cell is in progress through an examination of the kinetics of this process, and of the chemical and immunological nature of the rat adipose cell glucose transporter. The role of this translocation process in insulin's stimulatory action on glucose transport in rat diaphragm and the human adipose cell has now been suggested. A possible mechanism of insulin resistant glucose transport in the adipose cell in the aging rat model of obesity, with high fat:low carbohydrate feeding in the rat, and in the streptozotocin-induced diabetic rat model of insulin-dependent diabetes mellitus has been established with the demonstration of a relative depletion of the intracellular pool from which glucose transport systems are translocated to the plasma membrane in response to insulin in all three of these perturbed metabolic states.